Humans should not keep any animals in captivity that are larger in size than the average human. In fact, it is unethical to confine any animals for human entertainment, especially when alternatives for education and conservation exist. But particularly those that are larger in size, venues often do not have the required space to accommodate a cage or tank that is adequately sized for the animal. What are the impacts of captivity on animals ? We don't really know. We know that a characteristic of a healthy orca is a straight dorsal fin. But we see their dorsal fins curve in captivity, and we don't know why. We clearly do not understand the impacts of keeping animals in captivity, so the ethics could be even worse than we imagine. We should let most captive animals go. It is weird making them perform for human entertainment anyway...